On 14/07/2014 22:29, Spider wrote:
On 14/07/2014 13:54, Nick Maclaren wrote:
In article ,
News wrote:
On 11/07/2014 16:05, Spider wrote:
I've never used these bags in my compost bins before because I didn't
really trust them to break down. However, on buying a new compost
caddy, I find there are some inside.

Have others here found that these bags degrade well (completely
disappear would be good), or do they persist in the outdoor compost bin
months hence, only to be picked out by hand while riddling the compost?
Other irritants of this kind are tea bags and the supposedly
degradeable jiffy-type fibre pots.

When I first moved here, the previous residents had obviously used
plastic sacks all over the garden to suppress weeds. The garden was
scattered with thousands of shreds of black plastic bag:~((. This is
precisely what I do not wish to find in my usually perfect compost.

So the question is: do they really break down, or don't they?
Thanks for your time.

Not 100% sure but I assume so. We've been using small pale green ones
in an internal compost caddy for quite a long time. Although they are
obviously quite visible when they first go in a new compost section, I
don't recall seeing any bits in the older heaps. So I think they do
disintegrate but I'm not sure as to exactly how long they take.

It depends critically on the material. Pure polythene breaks down
very rapidly in ultraviolet light, and as soon as it absorbs water
and bacteria get to work on it. Commercial sheet has a lot of
additions to discourage this, so there is a gradation from some
plastic bags designed to degrade to polytunnel sheet, which is
very durable.

PVC is almost invariably non-degradable.


Regards,
Nick Maclaren.




Your mentioning ultraviolet light reminds me that my compost bins are
covered. I'm now having second thoughts. My bags may be meant to
degrade but, by excluding light, I may be removing an essential link in
the chain. Alas, the bags came in a plain cover, so no way of knowing
what they're made of. I may just have to experiment.

I wouldn't worry, just chuck them in, after all they wont get much light
in the bin, covered or not.
You could always leave them out in the sunlight for a week or so before
binning them